System for reception by television



Dec. 24, 1935. Q zw0 v 2,025,143

SYSTEM FOR RECEPTION BY TELEVISION Filed Aug. 15, 1950 I Fig.1:

/ INVENTOR Vladi mir: Klworg Kin.

HIS ATTORNEY Patented Dec. 24, 1935 SYSTEM FOR aecnr'rron BY TELEVISION Vladimir K. Zworykin, Collingswood, N. J., assignor, by mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application August 15, 1930, Serial N... 475,449

8 Claims.

- This invention relates to improvements in syste'ms for reception by television.

In the art of reception of an image by television, visibility has been limited, in constructions proposed heretofore, on account of inability to develop sufiicient light at the individual regions or spots of the composed image. While the amount of light or brightness of the image obtained has been sumcient for reception of an image in a relatively small frame, this is entire- 1y inadequate for development of an image over a surface or a screen of substantial area, such as that of the usual moving picture screens in theatres, for presentation to a large audience. In the various systems proposed heretofore, the brightness of the image is limited to the glow discharge of a glow tube or lamp as eflected by the received picture current.

It has been proposed to enlarge the relatively small image by projecting the same upon a screen. This expedient, however, has its limitations clue to the optical limitations or losses and, for this reason, it has been no solution of the problem of development of an image comparable in size and brightness with that of present day moving pictures.

The object of the present invention, therefore, is to provide an improved television receiving system wherein an image of any desirable size and brightness may be developed on a suitable screen structure and, generally, to provide for reception by television of an image comparable in size and brightness to that of present day moving'pictures.

In accordance with my invention, a local light source of substantially constant intensity is developed at a television receiving station, the light is utilized to illuminate a screen of any suitable size at the station, and the manner of illumination of the screen is controlled in accordance with variations in the received picture current to develop or compose an image on the screen.

More particularly, in accordance with my invention, a screen of any desirable size at a television receiving station is exposed to a local light source and a. cathode ray is developed and is utilized to control the degree or mode of illumination of the screen by the light in such manner as to compose or develop an image on the screen. My invention resides in an improved method and apparatus of the character hereinafter described and claimed.

For the purpose of illustrating my invention,

one embodiment thereof is shown in the drawing, wherein Fig. 1 is a diagrammatic view of a television receivsing system embodying the present improvemen Fig. 2 is an enlarged fragmentary view of one of the parts, looking toward the right in Fig. 1; Fig. 3 is a sectional view, the section taken on a line corresponding to the line 3-3 in Fig. 2;

Fig. 4 is a diagrammatic view, showing a modification;

Fig. 5 is an enlarged sectional view, the section taken on a line corresponding to line 5-5 in Fig. 4.

With reference to Fig. l, cathode ray tube apparatus, designated generally by reference numeral I0, is supported as shown between a screen i I of any desirable size and a local light source l2. is

A suitable lens or lens system I3 operates to pro= ject the light, developed at the source l2, in the form. of a beam of light, represented by the broken lines ll, onto the screen to illuminate the same. The light developed at the source I! is of substantially constant intensity.

The cathode ray tube ill is provided with a screen l5 having apertures l8 uniformly arranged over the same and through which the light passes to illuminate the exposed surface of screen ll. Similarly shaped elements ll of thin metallicmaterial such as tin foil, are attached at their upper edges I8 to the screen l5 for free pivotal movement with respect thereto over the apertures IE and are arranged, as shown more clearly in Fig. 3, for pivotal movement to different positions to vary the efiective areas of the individual apertures. These elements or valve members ll may be attached to the screen by suitable cementitious material, indicated by reference numeral l9, having a relatively low coefilcient of electrical conductivity.

The cathode ray tube is provided with the usual gun for directing the developed cathode ray onto the screen IS, the intensity ,of the ray being varied in accordance with the modulation of the picture current received by the receivin system, which system may be of any suitable ,construction. The system shown for receiving the transmitted signal impulses preferably comprises a suitable radio-frequency amplifier 2!", a suitable filter 22, and circuits 23 and 24 which may be of any suitable. and well-known construction or arrangement for supplying the respective deflective coils 26 and 26 with impulses causing the cathode ray 21 to scan the elements l1.

A line 28 connects the screen structure l5 to a suitable source of supply, indicated generally by reference numeral 29, which maintains this structure at a relatively high positive potential such, for example, as 4000 volts.

It is proposed to make the dimensions such that the cross section of the light beam I4 at the screen I5 embraces at least a 6-inch square. It is contemplated to so space and dimension the apertures I6 and the elements I! that in the 6- inch square there will be 48 parallel, uniformly spaced rows of the elements I'I, each row containing 48 uniformly spaced elements.

The operation of the system is as follows: The elements I1 are normally positively charged due to the high positive potential impressed upon the screen I5. The elements I! are therefore repelled from the surface of the screen I5 and normally are in position to permit the maximum amount of light to pass through the apertures It to illuminate the screen II. As the cathode ray scans the elements II, the individual elements are discharged in more or less degree, as the cathode ray strikes them, the degree of discharge, in any instance, depending upon the intensity of the ray, which in turn depends upon the strength at that instant of the received picture current. If the intensity of the ray is maximum, the discharge of the particular element II, with which the ray contacts at the instant, will be substantially complete, and this element, accordingly, will be attracted to the screen I5 and quickly moved to the fully closed position, indicated by the dotted line showing 30, to completely close the associated aperture I6 and completely cut off the light to the corresponding region or spot on the screen II illuminated through this aperture. For all intermediate values of ray intensity, the elements I! will be partly discharged in more or less degree and will assume corresponding intermediate positions between the normal, fully open position and the fully closed position, such action providing that the amount of light passing through the individual apertures is controlled to vary or control the illumination of corresponding regions or spots on the exposed surface of the screen II, whereby an image is developed or composed on this screen in accordance with modulation of the received picture current as the ray 21 scans the elements IT. For example, if the intensity of the ray 21 is only slightly below maximum intensity at the instant the ray strikes one of the elements H, the same will lose but a small part of its charge and will only partly close to a position such, for example, as that indicated by the dotted line showing 3|.

The coeficient of electrical conductivity of the cementitious material I9 is such as to provide leakage suflicient to permit complete recharge of a the elements I! within a period of time corresponding to one picture frame, that is, the period of time elapsing during one complete scanning of the screen I5 by the ray 27.

In the modification shown in Figs. 4 and 5, the screen I I is illuminated by the light from the source I2 reflected from a screen I 50 corresponding to the screen I5 in Fig. l, in which case the apertures I6 are omitted. The screen Iia has a polished surface .32. The elements 33, corresponding to the elements H in Fig. 3, have their surfaces treated or colored in any suitable manner, or these elements are of such material that substantially no light reflection will take place from the surfaces thereof. The elements 33, therefore, operate as masks to shut out the light in more or less degree from reflection to the screen' I I from the polished surface 32 of the screen I So, the degree of masking action of a particular element with which the ray 21 contacts at any instant corresponding to the ray intensity at that instant. As in Figs. 1 to 3, the elements 33 are normally repelled from the surface 32 of the screen I 5a to permit the maximum degree of illumination of the screenll. Aside from the fact that the screen I I is illuminated by reflection from the screen lie in Figs. 4 and 5, the action and the principle of operation thereof 11 are the same as in Figs. 1 to 3.

As a further modification, it is contemplated to omit the elements I1 and 33 and substitute for the screen I5 or lid 9. screen made of suitable material characterized by the fact that the same 15' is normally opaque, but upon being exposed to or struck by a cathode ray at any spot or region thereon, will become transparent to light in more or less degree at that spot or region, the degree of transparency varying in proportion and cor- 20 responding to the degree of intensity of the ray at that instant.

From the foregoing it will be seen that, in the present improved system, the light for the image is supplied by a local light source of substantially -33 constant intensity, the manner of illumination of the screen at the station being controlled in accordance with the modulation of the received picture current to develop or compose the image.

Although I have illustrated and descrlbedmy 30 invention as applicable to a. specific form of device, many other modifications will be apparent to those skilled in the art. It is my intention, therefore, that my invention be limited only in so far as is necessitated by the prior art and by 35 the spirit of the appended claims.

I claim as my invention:

1. In the art of television reception, the method of operation which comprises exposing a screen to a local light source of substantially'constant 40 intensity, developing a cathode ray, modulating the ray in accordance with incoming picture signals, and scanning said screen with the ray to vary the amount of light transmitted by the screen to develop a picture. 45

2. In a system for television reception, cathode ray apparatus comprising a tubeprovided with a screen capable of transmitting light under cathode ray bombardment and in amount proportional to the intensity of the ray, means for '50 developing a ray of electrons and directing the ray at said screen, means for varying the intensity of the ray in accordance with incoming picture signals, means for causing the my to scan said screen, and a second screen exterior of said tube 55 and disposed to receive light transmitted from said first-named screen.

3. In a system for television reception, screen structure, a light source of substantially constant intensity, structure having a light-reflecting surface and arranged to reflect the light from said surface to said screen, means including a cathode ray device associated with said second-named structure and operable to vary the degree of light-reflection from individual regions over 65 said surface, and means for controlling said firstnamed means.

4. In a system for television reception, screen structure, a local light source of substantially constant intensity for illuminating said structure, 7

and cathode-ray apparatus for controlling such illumination, said apparatus comprising a screen illuminated by the light from said source, means for developing a ray of electrons and directing the same at said screen, and means for deflecting the ray to cause the same to scan said screen, said screen being normally ineffective to transmit light beyond the'surface thereof, said screen being efiective at its individual elemental areas to transmit light beyond its surface and to said screen structure upon being struck by said ray and in amount substantially proportional to the intensity of the ray at the instant.

5. In a system for television reception, a local light source of substantially constant intensity,

screen structure, additional screen structure interposed between the latter and said light source and provided with apertures uniformly arranged over the same for illumination of said first-named structure by said light source through said apertures, valves associated respectively with the individual apertures and operable to vary the efiective areas thereof, means for actuating said valves in accordance with received signal effects, and comprising a tube containing said secondnamed screen structure and being provided with means for developing a ray of electrons and directing the same at said second-named screen structure, and means for deflecting said ray to cause the same to scan said second-named screen structure.

6. In apparatus of the character described, electrode structure, metallic elements arranged uniformly over said structure on one side thereof and pivotally connected thereto, means for developing a cathode ray directed onto said structure, and means for causing said ray to scan said elements.

7. In a system for television reception, means for developing a beam of light of substantially constant intensity, means for developing a cathode 5 ray, positively charged structure exposed directly to said beam and ray and capable of transmitting light under cathode ray bombardment and in amount proportional to the intensity of the ray, means for causing said ray to scan said structure, In and means for varying the intensity of the ray in accordance with incoming picture signals.

8. In a system for television reception, screen structure, a local light source of substantially constant intensity for illuminating said structure, 15 means for causing illumination of the respective elemental areas of said structure sequentially; said means comprising a cathode ray tube provided with a light valve in the form of a flat plate whose entire operating surface is illuminated con- 20 stantly and uniformly by the light from said source and by way of which such light reaches said screen structure, said tube provided with means for developing a ray 'of electrons focused on said surface and having means for varying the 25 intensity of the ray, means for deflecting'the ray simultaneously in different directions at relatively high and relatively low frequencies respectively to cause the ray to scan said surface; and means for applying received picture signals to the means for varying the intensity of the ray.

VLADIMIR K. ZWORYKIN. 

